How To Install Windows 8.1 From USB Flash Drive

Installing an operating system from a USB drive involves mainly three steps: preparing a bootable USB by transferring all files of the operating system onto the USB, enabling booting from USB on your PC, and then actually installing the operating system.

Long-time Windows users will know that preparing a bootable USB is relatively easy if you know a thing or two about the Command Prompt. Since not all users are comfortable with the command line, in this guide, we’re going to walk you through two methods with step-by-step instructions to install Windows 8.1 from a USB flash drive.

Method 1 involves preparing a bootable Windows 8.1 USB with the help of third-party software, and method 2 is for users who would like to prepare a bootable USB without using third-party tools (using Command Prompt). Note that both methods are compatible with 32-bit and 64-bit Windows.

Also read: How to Install Windows 8/8.1 from an external hard drive.

Method 1: Create a Windows 8.1 bootable USB with the help of Rufus

NOTE: In this guide, we are preparing a bootable USB on a Windows 8 PC, but you can use this method to create a bootable USB on Windows 7 as well.

Even though there are a bunch of good tools out there, including Microsoft’s own Windows 7 USB/DVD Download Tool, we’re going to use Rufus software, as it’s the best tool out there for the job.

Step 1: Connect the USB flash drive that you would like to install Windows on your PC and back up all data from the USB drive before proceeding further, as we’re going to erase all data by formatting it.

Step 2: Head over to this page and download the latest version of the Rufus tool. The download size is under 0.5 MB.

Step 3: Double-click on the downloaded Rufus.exe file to launch it (it’s a standalone tool). You will see a small dialog box asking, “Do you want to allow Rufus to check for application updates?” message. Click the Yes or No button to continue.

Step 4: Select your USB flash drive under the Device drop-down menu, select Partition scheme and target system type as MBR partition scheme for BIOS or UEFI computers, and select File system as NTFS.

NOTE: If you are preparing a bootable USB for a UEFI PC, you need to select Partition scheme and target system type as GPT partition scheme for UEFI computer and file system as FAT32. Note that UEFI doesn’t support the 32-bit version of Windows 8.1.

Step 5: Next, check the box named Create a bootable disk using, select ISO Image and then click the CD/DVD icon to browse to the Windows 8.1 ISO file. And if you have a Windows 8.1 DVD, we suggest you use Method 2.

Step 6: That’s it! Your bootable Windows 8.1 USB flash drive is ready! You can now connect to the PC, enable boot from USB under BIOS, and then start installing Windows 8.1.

Method 2: Preparing bootable USB using Command Prompt (without using extra tool)

Step 1: Open Command Prompt as administrator. To do this, in Windows 8, simultaneously press the Windows + X keys to see the Power Menu in the bottom left corner of the screen, click Command Prompt (admin), and then click Yes for the UAC prompt to launch the elevated prompt.

If you’re on Windows 7, open the Start menu, type CMD in the Start screen search box, and then simultaneously press Ctrl + Shift + Enter keys to run Command Prompt as administrator.

Step 2: Next, in the Command Prompt, type the following command:

Type DISKPART and press the Enter key.

Step 3: Type LIST DISK and then press the Enter key to see a list of all connected drives to your PC.

Here, you need to note down the Disk number of your USB flash drive that you wish to make bootable. For instance, in the below picture, the Disk number of my USB drive is “Disk 1”. We suggest you double-check your USB drive’s Disk number before proceeding to the next step, as we’re going to format it, and entering a wrong Disk number might erase other connected drives.

Step 4: Enter the following commands one by one and press Enter key after entering each command.

SELECT DISK 1 (replace “1” with your USB drive’s disk number)

CLEAN

CREATE PARTITION PRIMARY

SELECT PARTITION 1

ACTIVE

FORMAT FS=NTFS QUICK

ASSIGN

EXIT

Close the Command Prompt.

Step 5: Next, you need to either insert your Windows 8.1 installation DVD or mount your Windows 8.1 ISO file. If you’re on Windows 8, mounting the ISO file is fairly simple; right-click on the ISO file, and select the Mount option. When you mount the ISO file, you will see a new virtual drive in the Computer (My Computer).

And if you’re on Windows 7, please follow the instructions provided in our how to mount an ISO file in Windows 7 guide to successfully mount it.

Step 8: In this step, you need to copy all files, including autorun.ini file, from your Windows 8.1 DVD or mounted drive (containing files from ISO). That’s it! Your bootable Windows 8.1 USB drive is ready!

Good luck! You can reboot or connect your USB drive to the PC on which you wish to install Windows 8.1 and start installing the newest version of Windows.

And if your PC doesn’t support booting from USB, follow our how to install Windows from USB even if your PC doesn’t support it.